"[R]eviewing the terms of the fund documents is a critical aspect to a fiduciary's satisfaction of its fiduciary duties with respect to such investment.... [T]he terms of the fund documents may dictate whether an investment in the fund is an appropriate one for a particular ERISA investor, or whether it is flat out prohibited, or maybe just likely to result in a potential issue, such as a non-exempt prohibited transaction. Similarly, if the ERISA related terms of the fund documents are completely off market in a negative way, then that might make it more difficult for a plan fiduciary to make the case that investing in such a fund is prudent."